Tanning development



United States Patent C 3,293,035 TANNING DEVELOPMENT Albert Emiel Van Hoof, Berchem-Antwerp, and Georges Arthur Holvoet, Mortsel-Antwerp, Belgium, assignors to Gevaert Photo-Producten N.V., a Belgian company No Drawing. Filed Apr. 24, 1963, Ser. No. 275,203 Claims priority, applicato7r i7 gigiherlauds, Apr. 26, 1962, 9 12 Claims. (Cl. 96-35) This invention relates to an improved process for tanning development and to the light-sensitive materials and developing compositions used thereby.

It is generally known that an exposed gelatino silver halide emulsion layer is tanning developed by means of an alkaline developing solution containing pyrogallol, pyrocatechol or hydroquinone. It is known from the U.S. patent specification 2,967,772 that such a developing solution is quite easily oxidized by air, thus becoming strongly colored and difiicult to keep.

It is known that tanning developers are liable to aerial oxidation especially in alkaline medium. In order to avoid the use of an alkaline developing bath the exposed material is developed in an alkaline activating bath, after dipping in a neutral or slightly acid solution of the tanning developing substance. This developing method has the advantage that rapid exhaustion of the developing bath by aerial oxidation is avoided said method being, however, cu-mbrous.

In order to eliminate the disadvantages of the above methods, it was proposed to incorporate the tanning developer into the light-sensitive gelatino silver halide emulsion layer. In German patent specification 403,585 a silver halide emulsion layer is described containing in addition to a tanning developer an organic or inorganic acid (or acid salt thereof) with the exception of sulfurous acid, so that while retaining the tanning developing action, the keeping qualities of this layer are maintained. The development of such material occurs by dipping the exposed silver halide emulsion layer in an alkaline solution activating the development, e.g. in a solution of sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate.

It has, however, been stated that after keeping for a certain time, discoloration of the gelatino silver halide emulsion layer containing pyrogallol or pyrocatechol and occasionally of the paper support occurs. The discoloration is not uniform all over the surface but stained and especially intense on the margins of the light-sensitive sheet. Such stained material is no longer suited for refiectographic exposure through the back of the paper support since it does not transmit the light uniformly. On the areas corresponding with the stains the emulsion is less exposed and after tanning development less hardened. If this tanning developed materials is used for producing a gelatin relief, the parts of the emulsion corresponding to the stained areas which are exposed too little and not completely hardened, are partially removed when washing away the unhardened parts of the emulsion. When transferring the weak gelatin of such a tanning developed emulsion layer to another support e.g. paper by pressing the layer against said support, an irregular transfer is realized.

When using hydroquinone which is a very active tanning developer said discoloration does not arise.

The great disadvantage of hydroquinone as tanning developer compared to pyrocatechol and pyrogallol is the less selective tanning action. This occurs especially when incorporating the hydroquinone into the light-sensitive emulsion layer. According to P. Glafkides, Chimie Photographique, 2nd ed., p. 534, only pyrogallol gives a local hardening strictly corresponding to the exposed areas. Although hydroquinone shows certain advantages over pyrogallol and pyrocatechol as mentioned above, the unsharp hardening was the principal reason why it was not used as tanning developer to a larger scale. A localized hardening, strictly corresponding to the exposed areas, is especially important in the reproduction of documents and drawings and in screen exposure. The characters and lines appearing in texts and drawings possess generally a line-width smaller than 1 mm. The narrow undeveloped areas on the light-sensitive material corresponding to these lines are hardened together with the developed areas, especially when hydroquinone is used as tanning developer, so that they can neither be washed away with warm water nor be transferred to another support by pressing against said support. It is assumed that the hardening in said narrow undeveloped areas arises by the oxidized developer (quinone compound) it is formed in the exposed areas during the reduction of the silver halide, diffusing into said narrow undeveloped areas.

Since the hardening on the developed areas is very intense when using hydroquinone, the hardening on the undeveloped areas can be counteracted to a certain extent by incorporating into the emulsion or the bath a softening agent such as urea without decreasing considerably the hardening on the developed areas. It is not possible however, by such use of urea during tanning development to obtain a selectively hardened image pattern within a practically useful range of exposure. The softening effect of urea on gelatin is described in the U.S. patent specification 2,404,774.

Further it is known that sulfite ions from metabisulfites, sulfites or bisulfite restrain the tanning development. It is presumed that the oxidized developer reacts with sulfite and that as a result thereof the hardening by the reaction of the gelatin with the oxidized developing substance is inhibited. In this connection, P. Glafkides describes in Chimie Photographique, 2nd ed., page 534, that the hardening action is only complete in the presence of very little sulfite. As known, sulfite ions are incorporated into alkaline developing baths and light-sensitive gelatino emulsion layers in order to prevent aerial oxidation of the developer. It is, however, known that the sulfite content of alkaline developing solutions decreases rapidly by aerial oxidation so that a continuous control is required for keeping the sulfite content up to the level in view of obtaining selective hardening. Moreover, the use of large amounts of sulfite in the 1ight-sensitive gelatino silver halide emulsion layer gives rise to crystallization and fog (cf. U.S. patent specification 742,- 405, page 1, column 1, lines 16-23, and P. Glafkides, Chimie Photographique, 2nd ed., page 534).

It has now been found that a selective tanning development can be obtained using hydroquinone wherein the above mentioned disadvantages do not arise, when carrying out the development with hydroquinone in the presence of a primary amine and/or an aromatic hydroxy compound, both possessing in themselves no or practically no developing action. Said compounds may be added to the alkaline activating or developing solution and/or be incorporated into the light-sensitive gelatine silver halide emulsion layer. In the latter case they should be photographically inert.

As aromatic hydroxy compounds which according to the present invention in combination with hydroquinone increase the selectivity of the hardening are mentioned: u-naphthol, ,B-naphthol, polyhydroxybenzene compounds having at least two hydroxy groups in meta position with respect to each other such as resorcinol and phloroglucinol. The latter, however, is preferred.

The above mentioned aromatic hydroxy compounds may be added to the emulsion and/or developing bath with or without hydroquinone. They are, however, preferably incorporated into the gelatino silver halide emulsion layer together With some hydroquinone and bisulfite as stabilizer against aerial oxidation.

Primary amino compounds capable of reacting with quinone are all primary aliphatic and aromatic monoor polyamino compounds. The primary amino compounds used according to the invention must possess no or almost no developing activity and should preferably be well soluble in the alkaline developing or activating bath.

Compounds which are converted into primary amines when incorporated into the alkaline developing or activating bath (e.g. under the influence of the alkaline medium) and which possess no developing activity are also suited for being used according to the present invention.

According to the invention unsubstituted as well as substituted primary amines may be used. The primary amines are preferably substituted by water-solubilizing groups e.g. hydroxy groups, groups splitting off hydrogen ions such as carboxyl groups, sulfonic acid groups, phosphoric acid groups or the salts of these groups.

Examples of unsubstituted primary amines are: monomethylamine and monoethylamine. Unsubstituted aromatic primary amines are preferably not used because of their poisonness.

In order to avoid fog during storage the light-sensitive material, the unsubstituted primary amines are preferably added to the bath and not to the composition of the light-sensitive gelatino silver halide emulsion layer.

Examples of substituted primary amines compounds are: amino carboxylic acids such as amino acetic acid and amino succinic acid, amino sulfonic acids such as amino ethane sulfonic acid and 2,2-disulfo-4,4'diaminodiphenyl and aliphatic hydroxyamino compounds such as ethanolamine.

The primary amino compounds substituted with acid groups or acid groups in salt form are very suited for use in the gelatino silver halide emulsion layer as well as for use in developing or activating bath.

Concerning the possible reaction mechanism accord ing to which a more selective hardening is obtained, it is believed that the hardening restraining compounds react with the oxidized developer (quinone) and thereby prevent the diffusion of said quinone from the exposed to the unexposed areas.

It is evident that other additives such as developing activators, antifogging agents, sensitizers, anti-oxidizing agents and other compounds used in the composition of the light-sensitive material may also be incorporated into the composition of the gelatiuo silver halide emulsion layer.

In order to stabilize the light-sensitive gelatino silver halide emulsions wherein hydroquinone is incorporated, a compound splitting off bisulfite ions such as potassium metabisulfite (K S O is preferably incorporated therein. The amount of incorporated compound splitting 0ft bisulfite ions is preferably at most 0.5 mole per mole of hydroquinone in order to still obtain an appropriate hardening.

Examples of developing activators which may be added to the emulsion are the polyoxyalkylene derivatives described in the British patent specification 920,637 and in the Belgian patent specification 609,497 and 609,944.

The maximum amount of hardening restraining compounds used according to the present invention for still obtaining a sufiicient hardening is not the same for each combination. It was stated that the amount of hardening restraining compounds used in the present invention is preferably not higher than 30 to 35 mol percent based on the amount of hydroquinone available for development. If phloroglucinol is used, the amount of phlorogl-ucinol inc-orporated into the gelatino silver halide emulsion layer is preferably between 0.5 and 2.5 g. per g. of hydroquinone.

Tanning development according to the present invention may be carried out according to various methods, according to whether the compound for more selective hardening is present in the light-sensitive layer, in an alkaline developing bath or in an alkaline activating bath and the hydroquinone is incorporated in the developing bath or in the light-sensitive emulsion layer.

It is evident that the developing bath containing hydroquinone as well as the activating bath may contain the usual ingredients such as developing activators and antifogging agents in addition to the required amount of alkali for instance sodium carbonate.

As developing activators which may be added to these baths are especially suited those described in the French patent specification 1,269,312 such as p-nitrobenzy-lpyridinium chloride, 1,3-dipyridinium-propane dichloride and dipyridinium-methane dichloride. Suitable antifogging agents are: potassium bromide, benzotriazole and 1-phenyl5-mercaptotetrazole. These compounds, however, are not essential for the more selective tanning development according to the present invention.

When using a tanning developing bath containing hydroqui-none in the process according to the present invention, a compound capable of splitting off sulfite ions is preferably added to the bath in order to avoid aerial oxidation of the hydroquinone. Said compound is added in an amount of at most 0.4 mole per mole of .hydroquinone. A larger amount is undesirable since the tanning development is then too much restrained or even completely inhibited.

Especially for the tanning development of material destined for the manufacture of hectographic masters an amount of a softening agent e.g. urea is incorporated in the developing bath or in the activating bath.

The tanning development according to the present invention gives favorable results in the preparation of etching resists for use in photomechanical processes.

For that purpose a gelatin emulsion layer tanning developed according to the present invention is transformed by dissolving the weak emulsion parts (the so-called Washing away) in an etching resist. The manufacture of etching resists starting from an exposed gelatino silver halide emulsion layer is described e.g. in the Belgian patent specification 627,076.

Further the tanning development according to the present invention gives favorable results especially in the manufacture of hectographic masters (cf. the Belgian patent specifications 596,508 and 600,508 and the British patent specification 804,076). According to these processes the weak gelatin parts of the tanning developed emulsion layer have to be easily and selectively transferred to another support such as paper by pressing said layer against said support.

More particularly, the present invention presents an important progress especially in the manufacture of masters for spirit duplicating as described in the Belgian patent specifications 596,508 and 600,508 since using the compounds increasing the selectivity of the hardening according to the present invention in combination with a light-sensitive material of good stability and a stable activating bath, a sharp reproduction of characters or lines having a line width of 1 mm. is obtained.

According to an embodiment of the process described in the Belgian patent specification 596,508 a hectographic master is produced as follows:

(1) A negative image (e.g. a microfilm image) of an original is made;

(2) Said negative is projected on a gelatino silver halide emulsion layer;

(3) The exposed emulsion layer is tanning developed and a positive legible image is obtained;

(4) The tanning developed emulsion layer is pressed against a hectographic carbon paper and then both sheets stripped apart so that the weak gelatin covers the dyestutf layer of the carbon paper on the areas corresponding to the unexposed areas of the emulsion layer.

The carbon paper is used as master sheet on a usual spirit duplicator for making legible positive prints.

According to an embodiment of the process described in the Belgian patent specification 600,508 a master sheet for a spirit duplicator is produced by the following steps:

(1) A negative print of an original is made on the gelatino silver halide emulsion layer by reflectographic exposure through the back of the support; a

(2) The exposed emulsion layer is tanning developed;

(3) The tanning developed emulsion layer is pressed against a .hectographic carbon paper, occasionally while heating slightly;

(4) Both sheets are separated;

(5) The dyestuff layer of the carbon paper, image-wise covered with unhardened gelatin, is pressed against a sheet of art printing paper;

(6) After a few minutes both sheets are separated.

The unh-ardened gelatin has been transferred to the art printing paper and has pulled out dyestuff from the dyestutf layer. The art printing paper which after being separated from the carbon paper carries a laterally reversed image of the original composed of gelatin which is covered with dyestufi is used as hectographic master in a spirit duplicator.

In order to show the selectivity of the tanning development according to the present invention, a series of the same image-wise exposed light-sensitive materials was tanning developed in different developing compositions which in addition to hydroquinone contain a known hardening restraining substance such as potassium sulfite or a hardening restraining compound used according to the present invention.

The light-sensitive materials used for these developing tests were composed of a paper support of 135 g./sq. m. coated with a contrasty light-sensitive gelatino silver halide emulsion comprising per kg. of emulsion 64 g. of gelatin, 40 g. of silver chloride and 50 g. of urea.

The light-sensitive materials were reflectographically exposed through a step-wedge having a constant of 0.05 to a typographical text showing characters having a linewidth of 0.5 mm.

The developing solution, to which the hardening restraining compounds listed in the table below are added in turn, has the following composition:

Grams Sodium carbonate (anhydrous) 40 Urea 80 Dipyridinium-propane dichloride 1 Hydroquinone 5 Water up to 1000 ccs.

The exposed material is developed at 30 C. for 20 sec.

Number of exposure Amount of hardening restraining steps corresponding compound added per 1,000 ccs. of with the parts of text developing solution which are still washed away with water of 5 0.

None 0 2. g. of potassiunisulfite 2 10g. of mcthylarnine hydrochloride. 6 10 g. of monoetlianolrmine 6 10 g. of aminoacetic rcid 6 1 g. of phloroglucinoL 6 2 g. of resorcinol 3 Hereafter follows by way of illustration the description of the tanning development with combinations of developing solutions and the description of light-sensitive gelatino silver halide materials destined for producing hectographic masters for spirit-duplicating. These combinations may not at all be considered as limiting the scope of our invention.

(1) 1 kg. of gelatino silver halide emulsion according to the present invention and ready for coating comprises in addition to the required amount of water, antifogging agents, sensitizers and developing activators:

Grams Gelatin 65 Silver chloride 40 Hydroquinone 10 Potassium metabisulfite 8 Urea 55 Phloroglucinol I Said emulsion (emulsion A) is coated onto a paper support of 135 g./ sq. m. and dried. As comparison material a same emulsion containing, however, no phloroglucinol is prepared and coated (emulsion B).

Both emulsion layers are analogously reflectographicall exposed to a text the characters of which show a line-Width of at most 1 mm. Development occurs in the alkaline activating hath given below and containing each time another combination of hardening restraining compounds.

The adhesive power of the unh-ardened gelatin parts corresponding to the text, to the dyestuff layer of hectographic carbon paper is examined and the result are listed in the table below.

(2) The alkaline development activating solution to which each time one of the hardening restraining compounds listed in the table below is added has the following composition:

Grams Sodium carbonate (anhydrous) 40 Urea Water up to 1000 ccs.

The materials are developed at 30 C. for 20 sec.

Amount of hardening Adhesive power of carbon paper Fairly good. Bad.

2 g. of potassium sul- Bad.

fite.

2 g. of potassium sul- Good.

fite.

1 g. of phloroglucinoL. D0.

10 g. of aminoacetic Do.

acid.

10 g. oi aminoacetic Do.

For practical reasons combination 4 is not preferred. Thus it has been stated that when developing in an alkaline activating bath of combination 4, the adhesive power of the emulsion parts corresponding with the unexposed areas decreases rapidly when developing many negatives. The activating bath used in combination 6 is much more stable against exhaustion.

The following examples illustrate the present invention.

Exampe 1 To a light-sensitive gelatino silver halide emulsion comprising 75 g. of gelatin and 45 g. of silver chloride per kg. of emulsion, are successively added per kg. of emulsion a solution of 10 g. of hydroquinone in 50 ccs. of ethanol, a solution of 8 g. of potassium metabisulfite in 50 ccs. of water and 50 g. of urea. Then this emulsion is homogeneously mixed and [coated onto a baryta-coated paper of g./sq. m. in such a way that after drying 8 g. of gelatin are present per sq. m. of emulsion layer.

The dry emulsion :layer is reflectographioally exposed to a typographical text and developed for 20* sec. at 30 C. in an activating solution of the following composition:

G. Sodium carbonate (anhydrous) 40 Urea 80 Monoethanolamine 10 Potassium bromide 0.5 1,2-dipyridinumethane dichloride 1 Water up to 1000 ccs.

The undeveloped emulsion areas corresponding to the characters of the original can easily and selectively be washed away with water of about 50 C.

Example 2 A paper support of 135 g./sq. m. is coated with a thin layer from the following composition:

30 aqueous dispersion of colloidal silica liters 10 Ethanol do 1 Glycerol ccs- 150 After drying, about 6 g. of dry substance are present per sq. m. of layer. This layer serves as subbing layer for the gelatin-o silver halide emulsion layer which is prepared as follows.

To an emulsion containing 75 g. of gelatin and 45 g. of silver chloride per kg. are successively added per kg. of emulsion a solution of 10 g. of hydroquinone in 50 ocs. of ethanol, 2. solution of 8 g. of potassium metabisulfite in 50 ccs. of water and 50' g. of urea. Then the emulsion is homogeneously mixed and coated on the subbing layer in such a way that after drying 8 g. of gelatin are present per sq. m.

The emulsion layer is refiect-ograp-hically exposed to a typographical text and developed for 2.0 sec. at 30 C. in an activating solution of the following composition:

* G. Sodium carbonate (anhydrous) 40 Urea 80 Monoethanolamine 10 Potassium bromide 0.5 1,2-dipyridiniumethane dichloride 1 Water up to 1000 ccs.

The undeveloped emulsion areas corresponding to the characters of the original can easily and selectively be washed away with water of about 50 C.

Example 3 Example 1 is repeated with the exception that in the activating solution 10 g. of monoethanolamine are replaced by 2 g. of resorcinol.

The results are almost identical to those obtained in Example 1.

Example 4 To 1 kg. of a gelatino silver halide emulsion comprising 75 g. of gelatin and 45 g. of silver chloride per kg. are successively added a solution of 10 g. of hydroquino-ne and l g. of phloroglucinol in 50 cos. of ethanol, a solution of 8 g. of potassium metabisulfite in 50 cos. of distilled water and 50' g. of urea.

Then the emulsion is homogeneously mixed and coated onto a paper support provided with a layer of colloidal silica as described in Example 2. After refiectographic exposure to a line original the exposed material is developed for 20 sec. at 30 C. in a solution of the following composition:

G. Sodium carbonate (anhydrous) 40 Urea 8O Aminoacetic acid l 1,3-dipyridinium-propane dichloride 1 Potassium bromide 0.5 Sodium nitrate Water up to 1000 ocs.

The developed negative is immersed in water of about 50 C. so that the unhardened areas can easily be removed by rubbing with a rubber scraper.

Example 5 A tanning-developed negative obtained according to the method described in Example 4 is not treated with warm water but pressed with the emulsion layer against the dyestulf layer of a commercially available hectographic carbon p per, whereupon the materials pressed together are passed between two rubber pressure rollers. After 20 to 40 see. the two materials are stripped apart and the unhardened gelatin emulsion areas of the negative adhere to the dyestufi layer of the hectographic carbon paper.

The surface of the hectographic carbon paper should not be perfectly hydrophobic and hence before use it is occasionally degreased with naphtha and afterwards dried.

The hectographic carbon paper covered with the transferred weak gelatin is laid down with its back onto a smooth plate and pressed against a sheet of a glossy china clay-coated paper (art printing paper) by means of a rubber roller. After 2 min. of drying, the art printing paper is stripped apart from the carbon paper. By this treatment the gelatin adhering to the art printing paper pulls out a part of the dyestull from the dyestufr" layer of the carbon paper and so forms on the art printing paper a laterally reversed gelatin image covered with dyestuflf. This are printing paper can be used as hectographic master in a spirit duplicator. More than legible prints can be obtained.

Example 6 Example 4 is repeated with the exception that in the emulsion 1 g. of phloroglucinol is replaced by 3 g. of a-naphthol. The results are identical to those obtained in Example 4.

Example 7 The light-sensitive material of Example 6 is used for preparing a hectographic master as described in Example 5. Clear prints are obtained with said master.

Example 8 Example 4 is repeated with the exception that in the emulsion 1 g. of phloroglucinol is replaced by 2 g. of resorcinol. The results are identical to those obtaine in Example 4.

Example 9 l The light-sensitive material of Example 8 is used for preparing a hectographic master as described in Example 5. Prints with a good definition are obtained with said master.

Example 10 A light-sensitive material as described in Example 4 is developed in a solution of the following compositions:

G. Sodium carbonate (anhydrous) 40 Urea 80 Aminoethane sulfonic acid l0 1,3-dipyridinium-propane dichloride 1 Poatssium bromide 0.5 Sodium nitrate 5 Water up to 1000 ccs.

The developed material is further treated as in Example 5.

Example 11 A paper support of g./sq. m. is coated with a thin silica as described in Example 2. A silver halide emulsion is also prepared as in Example 2 with the exception, however, that moreover 5 g. of an aqueous solution of amino-acetic acid are added per kg. of emulsion.

The emulsion layer is reflectographically exposed to a typographical text and developed for 20 sec. at 30 C. in an activating solution of the following composition:

G. Sodium carbonate (anhydrous) 40 Urea 80 Water up to 1000 ccs.

By washing with farm water the developed gelatino silver halide emulsion layer is transformed into a gelatin relief image.

What we claim is:

1. In a process for producing a relief image in an imagewise exposed light-sensitive gelatino silver halide emulsion layer, the improvement which comprises subjecting said layer to tanning development with hydroquinone to form hardened and non-hardened areas, said tanning development being carried out in the presence of a harden ing inhibiting compound substantially free of silver halide developing activity and selected from the group consisting of (a) an aromatic hydroxy compound of the group consisting of a naphthol and a polyhydroxy benzene having at least two hydroxyl groups in meta position relative to one another, and

(b) a water-soluble primary amino compound of the group consisting of a lower aliphatic primary amine, an amino carboxylic acid, and an amino sulfonic acid; and removing at least a portion of the emulsion in the unhardened areas thereof to produce said relief image.

2. Process according to claim 1, wherein the hydroquinone is incorporated into the light-sensitive silver halide emulsion layer.

3. Process according to claim 1, wherein the hydroquinone for the tanning development is present in a tanning developing solution.

4. Process according to claim 2, wherein in addition to hydroquinone a compound capable of splitting off bistulfite ions is incorporated into the light-sensitive silver halide emulsion layer in a molar ratio of at most 1:2 based on the hydroquinone.

5. Process according to claim 3, wherein in addition to hydroquinone a compound capable of splitting off sulfite ions is incorporated into the tanning developing solution in a molar ratio of at most 0421 based on the hydroquinone.

6. Process according to claim 1, wherein said hardening inhibiting compound is present in a bath selected from the group consisting of an alkaline developing bath and an alkaline activating bath for said development.

7. Process according to claim 1, wherein said hardening inhibiting compound is an aromatic hydroxy compound incorporated in the light-sensitive gelatino silver halide emulsion layer.

8. Process according to claim 1, wherein as said hardening inhibiting compound, aminoacetic acid is used.

9. Process according to claim 1, wherein said inhibiting compound is phloroglucinol incorporated in the lightsensitive gelatino silver halide emulsion layer and aminoacetic acid in a tanning developing bath which contains said hydroquinone.

10. Process according to claim 1, wherein phloroglucinol and hydroquinone are incorporated in the lightsensitive gelatino silver halide emulsion layer and aminoacetic acid in an alkaline activating bath for said development.

11. Process according to claim 1, wherein the hardening inhibiting compound is used in an amount of at most 35 mol percent based on the amount of hydroquinone available for tanning development.

12. Light-sensitive photographic material for image wise exposure with light and development in an aqueous alkaline liquid comprising at least one silver halide emulsion layer and having incorporated therein:

(1) Hydroquinone in amount generally sufiicient to cause tanning development in the exposed areas of said layer in the presence of said aqueous alkaline liquid;

(2) A tanning inhibiting agent in an amount up to about 35 mole percent of said hydroquinone and generally sufficient to inhibit tanning development in the unexposed areas of said layer, said agent being free of developing activity and selected from the group consisting of;

(a) an aromatic hydroxy compound of the group consisting of a naphthol and a polyhydroxy benzene having at least two hydroxyl groups in meta position relative to one another, and

(b) a water-soluble primary amino compound of the group consisting of a lower aliphatic pri mary amine, an amino carboxylic acid, and an amino sulfonic acid; and

(3) A compound splitting off bisulfite ions in the presence of said liquid in an amount up to about 50 mol percent of said hydroquinone and generally sufiicient to stabilize said emulsion layer against aerial oxidation.

References Cited by the Examiner UNITED STATES PATENTS 2,165,421 7/1939 Sheppard et al. 96111 2,656,273 10/1953 Henn et al. 9675 2,834,676 5/1958 Stanley et al. 9666 2,835,575 5/1958 Cowden et al. 9628 2,865,745 12/1958 Chan et al. 9628 3,030,209 4/1962 Henn et al. 96111 3,043,688 7/1962 Weyerts et al. 96-28 3,080,230 3/ 1963 Haydn et al. 96-28 3,128,180 4/1964 Henn et al. 96111 XR NORMAN G. TORCHIN, Primary Examiner.

A. E. TANENHOLTZ, J. RAUBITSCHEK.

Assistant Examiners. 

1. IN A PROCESS FOR PRODUCING A RELIEF IMAGE IN AN IMAGEWISE EXPOSED LIGHT-SENSITIVE GELATINO SILVER HALIDE EMULSION LAYER, THE IMPROVEMENT WHICH COMPRISES SUBJECTING SAID LAYER TO TANNING DEVELOPMENT WITH HYDROQUINONE TO FORM HARDENED AND NON-HARDENED AREAS, SAID TANNING DEVELOPMENT BEING CARRIED OUT IN THE PRESENCE OF A HARDENING INHIBITING COMPOUND SUBSTANTIALLY FREE OF SILVER HALIDE DEVELOPING ACTIVITY AND SELECTED FROM THE GROUP CONSISTING OF (A) AN AROMATIC HYDROXY COMPOUND OF THE GROUP CONSISTING OF A NAPHTHOL AND A POLYHYDROXY BENZENE HAVING AT LEAST TWO HYDROXYL GROUPS IN META POSITION RELATIVE TO ONE ANOTHER, AND (B) A WATER-SOLUBLE PRIMARY AMINO COMPOUND OF THE GROUP CONSISTING OF A LOWER ALIPHATIC PRIMARY AMINE, AN AMINO CARBOXYLIC ACID, AND AN AMINO SULFONIC ACID; AND REMOVING AT LEAST A PORTION OF THE EMULSION IN THE UNHARDENED AREAS THEREOF TO PRODUCE SAID RELIEF IMAGE.
 12. LIGHT-SENSITIVE PHOTOGRAPHIC MATERIAL FOR IMAGE WISE EXPOSURE WITH LIGHT AND DEVELOPMENT IN AN AQUEOUS ALKALINE LIQUID COMPRISING AT LEAST ONE SILVER HALIDE EMULSION LAYER AND HAVING INCORPORATED THEREIN: (1) HYDROQUINONE IN AMOUNT GENERALLY SUFFICIENT TO CAUSE TANNING DEVELOPMENT IN THE EXPOSED AREAS OF SAID LAYER IN THE PRESENCE OF SAID AQUEOUS ALKALINE LIQUID; (2) A TANNING INHIBITING AGENT IN AN AMOUNT UP TO ABOUT 35 MOLE PERCENT OF SAID HYDROQUINONE AND GENERALLY SUFFICIENT TO INHIBIT TANNING DEVELOPMENT IN THE UNEXPOSED AREAS OF SAID LAYER, SAID AGENT BEING FREE OF DEVELOPING ACTIVITY AND SELECTED FROM THE GROUP CONSISTING OF; (A) AN AROMATIC HYDROXY COMPOUND OF THE GROUP CONSISTING OF A NAPHTHOL AND A POLYHYDROXY BENZENE HAVING AT LEAST TWO HYDROXYL GROUPS IN METAL POSITION RELATIVE TO ONE ANOTHER, AND (B) A WATER-SOLUBLE PRIMARY AMINO COMPOUND OF THE GROUP CONSISTING OF A LOWER ALIPHATIC PRIMARY AMINE, AN AMINO CARBOXYLIC ACID, AND AN AMINO SULFONIC ACID; AND (3) A COMPOUND SPLITTING OFF BISULFITE IONS IN THE PRESENCE OF SAID LIQUID IN AN AMOUNT UP TO ABOUT 50 MOL PERCENT OF SAID HYDROQUINONE AND GENERALLY SUFFICIENT TO STABILIZE SAID EMULSION LAYER AGAINST AERIAL OXIDATION. 